1. Field of the Invention
The present invention relates to a method and device for distinguishing patterns and, more particularly, to a pattern detection system such as a signal processing or signal analysis system for distinguishing true pattern responses from noise pattern responses. Typical patterns are edges in images. The present invention can be applied, for example, to the field of medical image analysis or to the field of robot vision.
2. Related Art
In order to distinguish true pattern responses from noise pattern responses in the output of a pattern detection system, the prior art usually thresholds the pattern contrast output of the pattern detection system, assuming that the noise level is known in any place of the input signal (see, for example, R. M. Haralick, "Digital Step Edges from Zero Crossing of Second Directional Derivatives", IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. PAMI-6, No. 1, 1984, pp. 58-68).
Alternatively, for a simple global noise estimation technique (see J. Canny, "A Computational Approach to Edge Detection", IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. PAMI-8, No. 6, 1986, pp. 679-698.
Especially if the known noise assumption is not valid, the selection of this pattern contrast threshold is difficult and is usually done manually by an operator. This manual selection sometimes needs to be done for every new input signal.